KR19980084359A - Comb filter without hanging dots - Google Patents

Abstract

A comb filter for separating a luminance signal and a color signal from a composite video signal is disclosed. The image separating unit separates the input composite image signal into a first luminance signal which is a low frequency low frequency image signal and a second luminance and color signal which is a high frequency high frequency image signal in which luminance and color signals are interleaved. The second signal separator separates the second luminance and color signals, which are the high frequency image signals separated by the image separator, into a second high frequency luminance signal and a second color signal. The 3.58 MHz detector detects a 3.58 MHz frequency component of the second luminance and color signals, which are the high frequency image signals separated by the image separator, and the second luminance and color signals, which are delayed by 1H. The controller controls the output of the luminance and color signals according to the 3.58 MHz frequency component detected by the 3.58 MHz detector, and the calculator calculates the second luminance signal and the second color signal separated by the second signal separator. . The selection output unit selects an output of the luminance and color signals in response to a control signal from the controller, and the luminance signal output unit outputs the selected luminance signal Y to the outside by calculating the luminance signal and the first luminance signal selected from the controller. do. By determining the presence or absence of the color carriers in the front and rear lines and selectively outputting a signal calculated according to the presence or absence of the color carriers, separation of luminance and color signals from the composite video signal can be improved.

Description

Comb filter without hanging dots

The present invention relates to a comb filter of a television receiver. More particularly, the present invention relates to a comb filter for adaptive comb filtering television signals to decode luminance and color signals without artifacts.

In general, the human eye is known that color information such as hue and saturation does not need to be as detailed as the information necessary for luminance in the image quality and image of the same sharpness. Therefore, the largest frequency band is allocated to the luminance signal in the frequency band of the television. On the other hand, for hue and saturation that do not correspond to the amount of change in luminance, the human eye should have 1/10 to 1/3 of the resolution required for brightness.

Color signals modulated as color subcarriers due to the above properties are put in a band much narrower than the luminance signal band. For example, in the NTSC system, an I signal component of a color signal modulated as a color subcarrier uses a 1.3 MHz band, and a Q signal component uses a 0.5 MHz band. Providing a wider band for the I signal component compared to the Q signal component of the color signal is because the I signal is better for color resolution.

Since the frequency of the color carrier is 3.58 MHz, the modulated color signal is interleaved on the high frequency sideband of the luminance signal to generate a composite image signal. The comb filter method is used to minimize the attenuation of the luminance signal and the interference by the luminance signal of the color signal when the luminance signal and the color signal interleaved with the luminance signal are separated from the composite image signal.

FIG. 1 is a circuit diagram showing the configuration of a conventional comb filter 10. An input terminal 11, one horizontal scanning time (H) delay circuit 12, a first subtractor 13, and a half amplifier ( 14), a band pass filter (BPF) 15, and a second subtractor 16.

Referring to the operation of the comb filter 10, when the composite video signal is input to the 1H delay circuit 12 through the input terminal 11, the 1H delay circuit 12 delays the input composite video signal by 1H. Output to the subtractor 13. The first subtractor 13 subtracts the 1H delayed composite video signal from the 1H delay circuit 12 from the current composite video signal input through the input terminal 11 to mutually attenuate the luminance signal component. A signal, that is, a color signal, is output to the half amplifier 14. Then, the half amplifier 14 amplifies the color signal output from the subtractor 13 by half and outputs it to the band pass filter 15. The band pass filter 15 filters the 1/2 amplified color signal from the 1/2 amplifier 14 and provides it to the second subtractor 16 and outputs it to the outside. The second subtractor 16 subtracts the filtered 1/2 amplified color signal from the band pass filter 15 from the current composite video signal input through the input terminal 11 to externally output the luminance signal Y. Will output

That is, in the comb filter 10, the color signal components of two consecutive horizontal scanning lines have a phase difference of 180 °. Accordingly, the comb filter 10 obtains only a color signal component by removing the luminance signal component from the composite image signal by calculating a signal difference between the input composite video signal and the currently input composite video signal with a 1H delay time. However, in the comb filter 10, a hanging dot phenomenon occurs on a screen due to vertical color shift, and a color signal is mixed with a luminance signal when the band passes, resulting in a dot crawl phenomenon. There is a problem.

Therefore, various methods for preventing such drawbacks have been proposed. The best known of these methods is the correlation adaptive comb filtering method.

2 is a circuit diagram showing the configuration of a conventional correlation adaptive comb filter 20. The correlated adaptive comb filter 20 includes an input terminal 21, first and second 1H delay circuits 22 and 23, first and second subtractors 24 and 25, first and second 1/2 amplifiers. (26, 27), first and second low pass filters (LPF) 28, 29, comparator 30, and data selector 31. As shown in FIG. The correlation adaptive comb filter 20 inputs a composite image signal of three consecutive horizontal scanning line lines, detects vertical correlation between them, and performs comb filtering toward a higher correlation.

The operation of the correlation adaptive comb filter 20 will be described below. When the composite video signal is input through the input terminal 21, the first 1H delay circuit 22 delays the input composite video signal by 1H to convert the 1H delay signal 32 into the second 1H delay circuit 23, Output to the first and second subtractors 24 and 25. The second 1H delay circuit 23 delays the 1H delayed composite video signal input from the first terminal 32 once more by 1H and outputs the 2H delayed composite video signal to the second adder 25. The first subtractor 24 subtracts the current composite video signal inputted through the input terminal 21 from the composite video signal delayed by 1H by the first 1H delay circuit 22 to thereby reduce the first subtracted signal 33. Is output to the first 1/2 amplifier 26 and the first low pass filter 28. In addition, the second subtractor 25 subtracts the 2H delayed composite video signal delayed by the second 1H delay circuit 23 from the 1H delayed composite video signal output from the first 1H delay circuit 22 to generate a second subtractor. The subtracted signal 34 is output to the second 1/2 amplifier 27 and the second low pass filter 29. The first half amplifier 26 and the second half amplifier 27 each amplify the first and second subtracted signals by half to respectively a first and second input terminals A and A of the selector 31. Output to the selector 31 through B).

The first low pass filter 28 and the second low pass filter 29 filter the first and second subtracted signals, respectively, through the first and second input terminals 35 and 36 of the comparator 30. Output to the comparator 30. The comparator 30 compares the amplitudes of the inputted first and second signals to generate a control signal of logic high when the amplitude of the first signal is greater than the amplitude of the second signal, and vice versa. The control signal of the row is output to the data selector 31 through the control signal input terminal S of the data selector 31.

When the logic high control signal is input from the comparator 30 through the control signal input terminal S, the selector 31 subtracts 1/2 amplified first from the first input terminal A. The signal is selected as the color signal C and output. On the contrary, when the control signal of the logic low is input, the selector 31 selects and outputs a half amplified second subtracted signal from the second input terminal B as the color signal C. Let's do it.

The color signal C selected by the selector 31 is again filtered by the band pass filter 15 to obtain a color signal as shown in FIG. 1, and the luminance signal is separated from the composite video signal by using the color signal. Done. Therefore, comb filtering is performed on the video signals of the two horizontal scanning lines having the higher vertical correlation, thereby preventing the occurrence of a hanging dot.

However, in the comb filter as described above, the color signals are separated based on the composite video signal of the adjacent line rather than separating the color signal from the composite video signal of the substantially horizontal scanning line, so that the interference between the lines and the hanging dots still exist.

An example of a comb filter is disclosed in US Pat. No. 5,225,899 (published July 6, 1993 to Park). The correlated adaptive luminance and color signal separation circuit according to the above-mentioned US patent is a circuit for separating the luminance signal and the color signal from the composite video signal used in color television, the vertical correlation of three consecutive horizontal scanning lines as well as the three Adaptive comb filter the composite video signal according to the vertical correlation by horizontal correlation of consecutive horizontal scanning lines, and then adaptive band filter the composite video signal according to the horizontal correlation, so that the composite video signal has a hanging dot and a dot It is configured to separate the luminance signal and the color signal without the cruel. According to the above-mentioned US patent, the vertical horizontal hanging dot can be removed by vertical horizontal correlation adaptive comb filtering. However, the hanging dots are still generated by the information difference of the composite video signal between the horizontal scanning lines which are correlated and adapted in the above-mentioned US patent.

The present invention has been made in view of the above problems, and an object of the present invention is to provide a comb filter capable of removing a hanging dot generated when a color signal is separated from a complex image signal of a horizontal scanning line.

1 is a circuit diagram showing the configuration of a conventional comb filter.

2 is a circuit diagram showing the configuration of a conventional correlation adaptive comb filter.

3 is a circuit diagram illustrating a comb filter according to an embodiment of the present invention.

4 is an operation principle diagram for describing a principle of generating a luminance signal of the selective output unit and the luminance signal output unit illustrated in FIG. 3.

<Explanation of symbols for main parts of drawing>

11, 101: input terminals 12, 22, 23, 210: 1H delay

13, 16, 24, 25, 230, 510: Subtractor 14, 26, 27, 620, 710: 1/2 amplifier

15: Band Pass Filter (BPF)

28, 29, 110: Low Pass Filter (LPF)

30: comparator 31: selector

100: image separation unit 200: second signal separation unit

220, 520, 720: Adder 300: 3.58 MHz detection unit

310, 320: 3.58 MHz detector 400: control unit

410: control box 500: calculator

600: selective output unit 610, 630: first and second switches

700: luminance signal output unit

In order to realize the above object, the present invention divides an input composite video signal into a first luminance signal which is a low frequency low frequency image signal and a second luminance and color signal which is a high frequency high frequency image signal in which luminance and color signals are interleaved. Image separation unit for; A second signal separation unit for separating a second luminance and color signal, which is a high frequency image signal separated by the image separation unit, into a second high frequency luminance signal and a second color signal; A 3.58 MHz detector configured to detect a 3.58 MHz frequency component of a second luminance and color signal, which is a high frequency image signal separated by the image separator, and a second luminance and color signal delayed by 1 H; A control unit for controlling the output of the luminance and color signals according to the 3.58 MHz frequency component detected by the 3.58 MHz detection unit; A calculator for calculating a second luminance signal and a second color signal separated by the second signal separator; A selection output unit for selecting an output of luminance and color signals in response to a control signal from the controller; And a luminance signal output unit configured to calculate and output the luminance signal selected from the controller and the first luminance signal.

According to the present invention described above, when the presence or absence of color carriers in the front and rear lines is determined, and when only the front and rear lines have color carriers, the degree of separation of the color and luminance signals from the composite video signal is switched by switching the calculated signal according to the presence or absence of the color carriers. It will be possible to improve.

Hereinafter, the present invention will be described in more detail with reference to the accompanying drawings.

3 is a circuit diagram illustrating a comb filter 800 according to an embodiment of the present invention.

Referring to FIG. 3, the comb filter in which the hanging dot is removed according to the present invention includes an image separator 100, a second signal separator 200, a 3.58 MHz detector 300, a controller 400, and a calculator 500. , The selective output unit 600, and the luminance signal output unit 700.

The image separator 100 includes a low pass filter 110 and a first subtractor 120. The composite image signal 102 input through the input terminal 101 is input to the low pass filter 110 and the first subtractor 120 of the image separator 100, respectively. The low pass filter 110 filters the first luminance signal Y _L , 112, which is a low frequency image signal composed only of the luminance signal by filtering a frequency signal of 3 MHz or less from the composite image signal input through the input terminal 101. The first subtractor 120 and the luminance signal output unit 700 are provided.

The first subtractor 120 is a first luminance signal Y which is a low frequency image signal of 3 MHz or less generated by the low pass filter 110 in the composite image signal 102 input through the input terminal 101. _L and 112 are subtracted to generate second luminance and color signals Y _H + C and 122, which are high frequency image signals interleaved with color signals and luminance signals, and generate the generated second luminance and color signals Y _H +. C and 122 are provided to the second signal separator 200 and the 3.58 MHz detector 300.

The second signal separator 200 includes a delay unit 210, a first adder 220, and a second subtractor 230.

The second signal separator 200 receives the second luminance and color signals Y _H + C and 122 output from the first subtractor 120 of the image separator 100 and receives the second luminance signal Y. _H , 222 and the second color signals C, 232 are separated. The second luminance and color signals 122 provided from the image separator 100 are transferred to the delay unit 210, the first adder 220, and the second subtractor 230 of the second signal separator 200. Is provided.

The delayer 210 receives the second luminance and color signal 122 output from the first subtractor 120, delays the second luminance and color signal 122 by 1H, and then delays the second luminance and the 1H delayed by the 1H. The color signal 212 is provided to the first adder 220, the second subtractor 230, and the 3.58 MHz detector 300.

The first adder 220 adds a second luminance signal Y _H , 222 obtained by summing a second luminance and color signal 122 and a second luminance and color signal 212 delayed by 1H to the calculator 500, and The selection output unit 600 is provided.

The second subtractor 230 subtracts the second luminance and color signal 212 delayed by 1H from the second luminance and color signal 122 to the operation unit 500 and the selection output. Provided to the unit 600.

The 3.58 MHz detector 300 includes a first 3.58 MHz detector 310 and a second 3.58 MHz detector 320. The first 3.58 MHz detector 310 detects 3.58 MHz frequency components A and 312 from the second luminance and color signal 122, and the second 3.58 MHz detector 320 is the 1H delayed second luminance. And 3.58 MHz frequency components B and 322 from the color signal 212 and provide the detected values to the controller 400, respectively.

The controller 400 is composed of a control box 410. The control box 410 includes the second luminance and color signals 122 and the 1H delayed second luminance and color signals extracted from the first 3.58 MHz detector 310 and the second 3.58 MHz detector 320. A control signal 412 for controlling the selection output unit 600 is generated according to the 3.58 MHz frequency component values A and B of 212. The generated control signal 412 is provided to the selection output unit 600.

The calculator 500 includes a third subtractor 510 and a second adder 520.

The third subtractor 510 subtracts the second color signals 232 and C output from the second subtractor 230 from the second luminance signals Y _H and 222 output from the first adder 220. The subtracted signal Y _H -C 512 is provided to the selection output unit 600. The second adder 520 may sum the second luminance signals Y _H and 222 output from the first adder 220 and the second color signals C and 232 output from the second subtractor 230. The sum signal Y _H + C 522 is provided to the selection output unit 600.

The selection output unit 600 includes a first switch 610, a first 1/2 amplifier 620, and a second switch 630.

The first switch 610 is provided with the first, second, and third input terminals T1, T2, and T3 in response to a control signal 412 output from the control box 410 of the controller 400. The second luminance signal (Y _H , 222) output from the first adder 220, the subtracted signal (Y _H -C, 512) output from the third subtractor 510, and the Any one of the sum signals Y _H + C and 522 output from the second adder 520 is selected and output to the luminance signal output unit 700.

The first half amplifier 620 amplifies the second color signals C and 232 output by the second subtractor 230 by one and a half times, thereby converting the second amplified second color signal to the second color signal. The signal is transmitted to the second input terminal T2 of the switch 630. The second switch 630 is provided with the first, second, and third input terminals T4, T5, and T6 in response to a control signal 412 output from the control box 410 of the controller 400. The second color signals C and 232 outputted to the second subtractor 230 and the 1/2 amplified second color signals outputted from the first 1/2 amplifier 620 are input to the second subtractor 230. Selectively output to the color signal output terminal (C).

The luminance signal output unit 700 includes a second half amplifier 710 and a third adder 720. The second 1/2 amplifier 710 amplifies the signal output from the first switch 610 of the selection output unit 1/2 by 1/2 times to convert the half amplified luminance signal into the third adder 720. To provide. The third adder 720 is amplified by the first luminance signal 112 output from the low pass filter 110 of the image separation unit 100 and the second 1/2 amplifier 710. The obtained luminance signal 712 is summed and output to the luminance signal output terminal Y. FIG.

4 is an operation principle diagram for describing a principle of generating a luminance signal of the selective output unit and the luminance signal output unit illustrated in FIG. 3. The first switch 610 and the second switch 630 of the selection output unit 600 and the second 1/2 amplifier 710 and the third adder 720 of the luminance signal output unit 700 are disposed. A detailed operation principle of generating the luminance signal mainly will be described with reference to FIG. 4.

Referring to FIG. 4, when the front line B1 is only the luminance signal Y and the rear line A1 is the luminance and color signal Y + C, the second luminance signal Y _H and the color signal C ) Is subtracted, a 2Y signal is output. Further, when the front line B2 is the signal YC subtracted from the luminance signal Y and the rear line A2 is the luminance signal Y only, the second luminance signal Y _H and the color signal ( When C) is added up, a 2Y signal is output. After the output luminance signal 2Y is amplified 1/2 times, the luminance signal 2Y is summed with the low-frequency luminance signal to output a final luminance signal.

This is illustrated in connection with the first switch 610 and the second switch 630 of the selection output unit 600 as follows.

A B First switch Second switch 0 0 First input (T1) First input (T4) One One First input (T1) First input (T4) One 0 Second input (T2) Second input (T5) 0 One Third input (T3) Third input (T6)

Therefore, according to the above configuration, it is possible to improve the separation of luminance and color signals from the composite video signal by judging the presence or absence of color carriers in the front and rear lines and selectively outputting a signal calculated according to the presence or absence of color carriers.

As described above, according to the present invention, the presence or absence of color carriers in the front and rear lines can be detected from the image signal, and the luminance and color signals can be separated according to the detected color carriers, thereby effectively removing the hanging dots appearing when the luminance and color signals are separated. .

Although this invention was demonstrated concretely by the said Example, this invention is not restrict | limited by this, A deformation | transformation and improvement are possible within the normal knowledge of a person skilled in the art.

Claims (9)

An image separator 100 for separating the input composite image signal into a first luminance signal that is a low-frequency low-frequency image signal and a second luminance and color signal that is a high-frequency high-frequency image signal in which luminance and color signals are interleaved; A second signal separator 200 for separating a second luminance and color signal, which is a high frequency image signal separated by the image separator, into a second high frequency luminance signal and a second color signal; A 3.58 MHz detector 300 for detecting a 3.58 MHz frequency component of a second luminance and color signal, which is a high frequency image signal separated by the image separator, and a second luminance and color signal delayed by 1 H; A controller 400 for controlling the output of the luminance and color signals according to the 3.58 MHz frequency component detected by the 3.58 MHz detector; A calculator 500 for calculating a second luminance signal and a second color signal separated by the second signal separator; A selection output unit 600 for selecting an output of luminance and color signals in response to a control signal from the controller; And And a luminance signal output unit (700) for calculating and outputting the luminance signal selected from the controller and the first luminance signal. The image separating unit 100 of claim 1, A 3 MHz low pass filter 110 for filtering low frequency signals from the input composite video signal; And And a first subtractor 120 for generating a second luminance and color signal 122 that is the high frequency image signal by subtracting the low frequency image signal filtered by the low pass filter from the input composite image signal. Comb filter. The method of claim 1, wherein the second signal separation unit 200 A delay unit (210) for receiving the second luminance and color signal (122) and delaying the signal by 1H; A first adder (220) for calculating the second luminance and color signal (122) and the 1H delayed second luminance and color signal (212); And And a second subtractor (230) for calculating the 1H delayed second luminance and color signal (212) from the second luminance and color signal (122). According to claim 1, wherein the 3.58MHz detector 300 A first 3.58 MHz detector (310) for detecting a 3.58 MHz frequency component (A, 312) from said second luminance and color signal (122); And And a second 3.58 MHz detector (320) for detecting a 3.58 MHz frequency component (B, 322) from said 1 H delayed second luminance and color signal (212). The control unit 400 of claim 1, wherein the control unit 400 detects the 3.58 MHz frequency components A and 312 and the second 3.58 MHz that are detected by the first 3.58 MHz detector 310 from the second luminance and color signal 122. And a controller 410 for generating a 3.58 MHz frequency component (B, 322) control signal 412 detected from the second luminance and color signal 212 delayed by the detector 320 by 1H. filter. The method of claim 1, wherein the calculation unit 500 A third subtractor 510 for calculating a second luminance signal and a second color signal separated by the second signal separator 200; And And a second adder (520) for calculating the second luminance signal and the second color signal separated by the second signal separator (200). The method of claim 1, wherein the selection output unit 600 is First, second, and third input terminals T1, T2, and T3, the first, second, and third inputs in response to a control signal 412 output from the controller 400; A first switch 610 for selectively outputting signals input to the terminals T1, T2, and T3 to the luminance signal output unit 700; A first half amplifier 620 for amplifying the second color signals C and 232 output by the second signal separator 200 by a factor of 1/2; And The first, second, and third input terminals T4, T5, and T6, the first, second, and third inputs in response to a control signal 412 output from the controller 400; And a second switch (630) for selectively outputting the signals input to the terminals (T4, T5, and T6) to the luminance signal output unit (700). The method of claim 1, wherein the luminance signal output unit 700 A second 1/2 amplifier 710 for amplifying the signal output from the first switch 610 1/2 times; And A third adder 720 for calculating a first luminance signal 112 which is a low frequency image signal filtered by a low pass filter in the input composite image signal and a signal output from the second 1/2 amplifier 710 Comb filter, characterized in that consisting of. The method of claim 7, wherein the selection output unit 600 is delayed by 1H by the 3.58MHz frequency components A and 312 detected by the first 3.58MHz detector 310 and the second 3.58MHz detector 320. For the 3.58 MHz frequency component B, 322 detected from the second luminance and color signal 212, When A is logic low and B is logic low, a first input terminal T1 connected when A is logic high and B is logic high, and a second connected when A is logic high and B is logic low A first switch 610 including an input terminal T2 and a third input terminal T3 connected when A is logic low and B is logic high; And When A is logic low and B is logic low, the first input terminal T4 connected when A is logic high and B is logic high, and the second connected when A is logic high and B is logic low And a second switch (630) including an input terminal (T5) and a third input terminal (T6) connected when A is logic low and B is logic high.